I don't really get affected by cartoon deaths too much unless there's something that really pisses me off. But there have been a couple to really get under my skin.
Fullmetal Alchemist
Naruto
Death Note
Fullmetal Alchemist
Let me state that I am an animal person. I like animals over people. (I'm not in a group or anything but yeah..) Nina's death, while I understand why Scar did it, it truly pissed me off to the point to where I gave up on the series. Had I continue watching it I would've/could've went off on everybody that said something to me. (bad or nice, I probably would've taken a swing at you.)
Naruto
Kakashi. The only reason I had a problem with Kakashi's death was because of the way he supposedly died. I wouldn't have minded seeing him kick the bucket but at least let him go out with a bang instead of dying to chakra exhaustion.
Death Note
Rem. I'm not a fan of hers, but the way she died had me hating Kira.